Summary:
Fix#23849. When setting a semi-transparent background on text, it becomes obvious that we are drawing the background color twice. Since background color is handled by the view, we should not need to draw the glyph background color too.
| Before | After |
| ------------- |-------------|
|<img src="https://i.imgur.com/8JGpKTC.png" width="300"> | <img src="https://imgur.com/qjKU9Ze.png" width="300">
[iOS] [Fixed] - Semi-transparent backgrounds on text
Pull Request resolved: https://github.com/facebook/react-native/pull/23872
Differential Revision: D14430501
Pulled By: shergin
fbshipit-source-id: 19743415b2d20a3b941b1c80bd7b47144e929458
bbf715685e
